This invention relates to a process and composition for imparting electrical charges to gaseous atmospheres, such as air streams. More particularly, electrical charges are imparted to a gaseous atmosphere by spraying an aqueous solution containing a quaternary ammonium compound and a surfactant into the stream.
Friction between objects of different molecular structures creates static electric charges. This problem is particularly acute in the textile industry where certain textile processing operations require frictional contact between a yarn and various mechanical devices. Depending upon the nature of the yarn, positive or negative charges build up and often lead to deleterious consequences. A safe, economical means of controlling both positive and negative static electricity is, therefore, of considerable interest to the textile industry.
Many attempts have been made in the past to neutralize static electricity. In the textile industry basically two approaches have been employed. One approach involves Corona discharge electrostatic devices and the other employs chemical additives, which are introduced into air-wash systems existing in textile plants. Regardless of the specific device employed, the effectiveness of these methods hinges on their ability to introduce sub-microscopic charged particles into the immediate vicinity where objectionable static build-up occurs.
Corona discharge devices suffer from their inability to produce long-lived charges on the particles they depend upon. The short-lived charges help, but not enough to satisfy the needs in a textile plant.
Most anti-static formulations marketed for use in air-washers suffer from a lack of flexibility in that they are only able to solve half the problem existing in the control of static electricity; that is to say, they are capable of neutralizing positive static charges at the exclusion of negative static charges. They have not been found to be suitable for simultaneously neutralizing positive and negative static charges.
A composition and method for electrifying a gaseous atmosphere are disclosed in U.S. Pat. No. 3,924,157, to Peters and McAmish and assigned to the assignee of the present application. This patent teaches that an aqueous solution of borax and a surfactant can be sprayed into a gaseous stream to impart a positive electrical charge to the stream. In other words, a net positive charge is imparted to the gas stream using this composition. The composition and method have enjoyed a degree of commercial success, but because the composition contains a relatively large amount of borax, it is necessary to market the composition in paste or powder form. To market it in solution form would require such a large amount of water as to make it uneconomical to ship and handle. It would be ideal if a composition capable of neutralizing both positive and negative static charges could be provided. It would also be ideal if such a composition could be made suitable for marketing in liquid form.
U.S. Pat. No. 3,939,080 and U.S. Pat. No. 3,984,731 also disclose a composition and a method for neutralizing static electricity. These patents teach that dodecylbenzyl triethyl ammonium chloride can be added to an air-washer that delivers a flow of air to a room in which static electricity is present. The composition suffers the same deficiencies noted with respect to other anti-static formulations for use in air-washers; namely, only one type of static charge is neutralized to any great extent and in this case it is the negative static charges. Thus, dodecylbenzyl triethyl ammonium chloride operates in a manner similar to a mixture of borax and a surfactant in that each imparts a predominantly net positive charge to an air stream.
Other methods for imparting a charge to a gaseous atmosphere are also known in the art, but each has its unique limitations. For example, merely contacting a gaseous stream with a water spray has been found sufficient to impart an electrical charge to the stream.
In other cases, a high electrical potential is applied to a water spray before being contacted with the gaseous stream. These methods have not proved entirely satisfactory because of the electrical energy requirement, the safety hazards involved and periodic equipment breakdowns.
Still other methods involve the use of radioactive substances. These methods have not proved entirely satisfactory because of the cost of the radioactive materials and the hazards involved in handling such materials. Furthermore, systems employing radioactive materials can be rather costly because of the safeguards that must be provided.
Thus, there exists a need in the art for a process and composition for discharging both positive and negative static build-up. The process and composition should be of relatively low cost, fairly simple and safe to use without the need for costly equipment. The process and composition should ideally be suited for use with existing air-wash systems in textile plants. Preferably, the composition should be marketable in liquid form for ease of handling and for ease of feeding to spray systems. The composition should also have a long shelf life.